A 3rd generation partnership project (3GPP) long term evolution (LTE) which is an improved universal mobile telecommunications system (UMTS) is introduced as 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and uses single carrier-frequency division multiple access (SC-FDMA) in uplink. A multiple input multiple output (MIMO) having maximum four antennas is employed. Recently, a discussion on LTE-Advanced (LTE-A) which is evolved 3GPPP LTE is being developed.
A minimization of driving tests (MDT) is to test by operators for coverage optimization by using a terminal instead of a vehicle. The coverage is varied according to a location of a base station, an arrangement of neighboring buildings, and a use environment of a user. Therefore, the operator needs to periodically perform a driving test, which consumes a lot of cost and resources. The MDT measures the coverage by the operator using the terminal.
The operator may draft a coverage map indicating availability of a service over an overall service area of the operator and distribution of a quality of the service by summarizing the MDT measurement received from a plurality of terminals, thereby utilizing the coverage map for operating and optimizing the network. For example, when a coverage problem of a particular area is reported from the terminal, the operator may increase transmission power of the base station which provides a service to the corresponding area to expand the coverage of a corresponding cell.
Generally, evolution of the network and evolution/replacement of the terminal are gradually carried out. As a result, it is more common that a heterogeneous network in which a plurality of RATs coexists is disposed rather than a homogeneous network in which a single radio access technology (RAT) is used. Also, a terminal which supports the heterogeneous network is widely distributed.
The RAT refers to a wireless technology based on a specific standardization. Specifically, the RAT includes GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), and Evolved-UTRAN (E-UTRAN).
In order for the terminal to receive an optimized service in the heterogeneous network, a wireless environment of the heterogeneous network also needs to be optimized. However, optimizing RATs having a widely different service area or channel characteristic is not easy.
Due to a characteristic of the MDT which is performed for optimizing the service, the measurement of various RAT needs to be identified.